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Commit aa6083ed authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARCv2: SMP: ARConnect debug/robustness 



- Handle possible interrupt coalescing from MCIP
- chk if prev IPI ack before sending new

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 82fea5a1

arch/arc/Kconfig

+12 −3
Original line number Diff line number Diff line
@@ -448,9 +448,10 @@ menuconfig ARC_DBG 
	bool "ARC debugging"

	default y



if ARC_DBG



config ARC_DW2_UNWIND

	bool "Enable DWARF specific kernel stack unwind"

	depends on ARC_DBG

	default y

	select KALLSYMS

	help
@@ -464,18 +465,26 @@ config ARC_DW2_UNWIND 


config ARC_DBG_TLB_PARANOIA

	bool "Paranoia Checks in Low Level TLB Handlers"

	depends on ARC_DBG

	default n



config ARC_DBG_TLB_MISS_COUNT

	bool "Profile TLB Misses"

	default n

	select DEBUG_FS

	depends on ARC_DBG

	help

	  Counts number of I and D TLB Misses and exports them via Debugfs

	  The counters can be cleared via Debugfs as well



if SMP



config ARC_IPI_DBG

	bool "Debug Inter Core interrupts"

	default n



endif



endif



config ARC_UBOOT_SUPPORT

	bool "Support uboot arg Handling"

	default n

arch/arc/kernel/mcip.c

+44 −4
Original line number Diff line number Diff line
@@ -33,27 +33,67 @@ void mcip_init_smp(unsigned int cpu) 
static void mcip_ipi_send(int cpu)

{

	unsigned long flags;

	int ipi_was_pending;



	/*

	 * NOTE: We must spin here if the other cpu hasn't yet

	 * serviced a previous message. This can burn lots

	 * of time, but we MUST follows this protocol or

	 * ipi messages can be lost!!!

	 * Also, we must release the lock in this loop because

	 * the other side may get to this same loop and not

	 * be able to ack -- thus causing deadlock.

	 */



	do {

		raw_spin_lock_irqsave(&mcip_lock, flags);

		__mcip_cmd(CMD_INTRPT_READ_STATUS, cpu);

		ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK);

		if (ipi_was_pending == 0)

			break; /* break out but keep lock */

		raw_spin_unlock_irqrestore(&mcip_lock, flags);

	} while (1);



	__mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu);

	raw_spin_unlock_irqrestore(&mcip_lock, flags);



#ifdef CONFIG_ARC_IPI_DBG

	if (ipi_was_pending)

		pr_info("IPI ACK delayed from cpu %d\n", cpu);

#endif

}



static void mcip_ipi_clear(int irq)

{

	unsigned int cpu;

	unsigned int cpu, c;

	unsigned long flags;

	unsigned int __maybe_unused copy;



	raw_spin_lock_irqsave(&mcip_lock, flags);



	/* Who sent the IPI */

	__mcip_cmd(CMD_INTRPT_CHECK_SOURCE, 0);



	cpu = read_aux_reg(ARC_REG_MCIP_READBACK);	/* 1,2,4,8... */

	copy = cpu = read_aux_reg(ARC_REG_MCIP_READBACK);	/* 1,2,4,8... */



	__mcip_cmd(CMD_INTRPT_GENERATE_ACK, __ffs(cpu)); /* 0,1,2,3... */

	/*

	 * In rare case, multiple concurrent IPIs sent to same target can

	 * possibly be coalesced by MCIP into 1 asserted IRQ, so @cpus can be

	 * "vectored" (multiple bits sets) as opposed to typical single bit

	 */

	do {

		c = __ffs(cpu);			/* 0,1,2,3 */

		__mcip_cmd(CMD_INTRPT_GENERATE_ACK, c);

		cpu &= ~(1U << c);

	} while (cpu);



	raw_spin_unlock_irqrestore(&mcip_lock, flags);



#ifdef CONFIG_ARC_IPI_DBG

	if (c != __ffs(copy))

		pr_info("IPIs from %x coalesced to %x\n",

			copy, raw_smp_processor_id());

#endif

}



volatile int wake_flag;

arch/arc/kernel/smp.c

+16 −4
Original line number Diff line number Diff line
@@ -278,8 +278,10 @@ static void ipi_cpu_stop(void) 
	machine_halt();

}



static inline void __do_IPI(unsigned long msg)

static inline int __do_IPI(unsigned long msg)

{

	int rc = 0;



	switch (msg) {

	case IPI_RESCHEDULE:

		scheduler_ipi();
@@ -294,8 +296,10 @@ static inline void __do_IPI(unsigned long msg) 
		break;



	default:

		pr_warn("IPI with unexpected msg %ld\n", msg);

		rc = 1;

	}



	return rc;

}



/*
@@ -305,6 +309,7 @@ static inline void __do_IPI(unsigned long msg) 
irqreturn_t do_IPI(int irq, void *dev_id)

{

	unsigned long pending;

	unsigned long __maybe_unused copy;



	pr_debug("IPI [%ld] received on cpu %d\n",

		 *this_cpu_ptr(&ipi_data), smp_processor_id());
@@ -316,11 +321,18 @@ irqreturn_t do_IPI(int irq, void *dev_id) 
	 * "dequeue" the msg corresponding to this IPI (and possibly other

	 * piggybacked msg from elided IPIs: see ipi_send_msg_one() above)

	 */

	pending = xchg(this_cpu_ptr(&ipi_data), 0);

	copy = pending = xchg(this_cpu_ptr(&ipi_data), 0);



	do {

		unsigned long msg = __ffs(pending);

		__do_IPI(msg);

		int rc;



		rc = __do_IPI(msg);

#ifdef CONFIG_ARC_IPI_DBG

		/* IPI received but no valid @msg */

		if (rc)

			pr_info("IPI with bogus msg %ld in %ld\n", msg, copy);

#endif

		pending &= ~(1U << msg);

	} while (pending);